Radar based mapping and localization for autonomous vehicles

ABSTRACT

In an example method, a vehicle configured to operate in an autonomous mode could have a radar system used to aid in vehicle guidance. The method could include transmitting at least two signal pulses. The method further includes, for each transmitted signal pulse, receiving a reflection signal associated with reflection of the respective transmitted signal pulse. Each reflection signal may be received when the apparatus is in a different respective location. Additionally, the method includes processing the received reflection signals to determine target information relating to one or more targets in an environment of the vehicle. Also, the method includes correlating the target information with at least one object of a predetermined map of the environment of the vehicle to provide correlated target information. Yet further, the method includes storing the correlated target information for the at least one object in an electronic database.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/503,131, filed on Jul. 3, 2019, which is a continuation ofU.S. patent application Ser. No. 15/013,233 (now U.S. Pat. No.10,386,480), filed on Feb. 2, 2016, the entire contents of all areherein incorporated by reference.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Radio detection and ranging (RADAR) systems can be used to activelyestimate distances to environmental features by emitting radio signalsand detecting returning reflected signals. Distances to radio-reflectivefeatures can be determined according to the time delay betweentransmission and reception. The radar system can emit a signal thatvaries in frequency over time, such as a signal with a time-varyingfrequency chirp, and then relate the difference in frequency between theemitted signal and the reflected signal to a range estimate. Somesystems may also estimate relative motion of reflective objects based onDoppler frequency shifts in the received reflected signals.

Some example automotive radar systems may be configured to operate at anelectromagnetic wave frequency of 77 Giga-Hertz (GHz), which correspondsto millimeter (mm) electromagnetic wave lengths (e.g., 3.9 mm for 77GHz). The radar system may be configured to transmit a radio waveformthat that include a linear frequency modulation (LFM).

SUMMARY

In a first aspect, a method is provided. In some embodiments, the methodincludes transmitting, by a radar unit of a vehicle, at least two signalpulses. The method further includes for each transmitted signal pulse,receiving, by the radar unit, a reflection signal associated withreflection of the respective transmitted signal pulse. Each reflectionsignal may be received when the vehicle is in a different respectivelocation. Additionally, the method includes processing the receivedreflection signals to determine target information relating to one ormore targets in an environment of the vehicle. Also, the method includescorrelating the target information with at least one object of apredetermined map of the environment of the vehicle to providecorrelated target information. Yet further, the method includes storingthe correlated target information for the at least one object in anelectronic database.

In a second aspect, another method is provided. The method includestransmitting, by a radar unit of a vehicle, at least two signal pulses.The method further includes for each transmitted signal pulse,receiving, by the radar unit, a reflection signal associated withreflection of the respective transmitted signal pulse. Each reflectionsignal may be received when the vehicle is in a different respectivelocation. Additionally, the method includes processing the receivedreflection signals to determine target information relating to one ormore targets in an environment of the vehicle. Also, the method includescorrelating the target information with predetermined target informationto provide correlated target information. Yet further, the methodincludes determining a location of the vehicle based on the correlatedtarget information. And, the method also includes controlling anautonomous vehicle based on the determined location of the vehicle.

In a third aspect, an apparatus is provided. The apparatus includes aradar unit. The radar unit has a transmitter configured to transmit atleast two signal pulses. The radar unit also has a receiver configuredto receive, for each transmitted signal pulse, a reflection signalassociated with reflection of the respective transmitted signal pulse,where each reflection signal is received when the apparatus is in adifferent respective location. The apparatus also includes a processingunit. The processing unit is configured to process the receivedreflection signals to determine target information relating to one ormore targets in an environment of the apparatus. The processing unit isalso configured to correlate the target information with predeterminedtarget information to provide correlated target information. Theprocessing unit is further configured to determine a location of theapparatus based on the correlated target information. And, theprocessing unit is also configured to control an autonomous vehiclebased on the determined location.

In a fourth aspect, another apparatus is provided. In some embodiments,the apparatus includes means for transmitting at least two signalpulses. The apparatus further includes for each transmitted signalpulse, means for receiving a reflection signal associated withreflection of the respective transmitted signal pulse. Each reflectionsignal may be received when the apparatus is in a different respectivelocation. Additionally, the apparatus includes means for processing thereceived reflection signals to determine target information relating toone or more targets in an environment of the apparatus. Also, theapparatus includes means for correlating the target information with atleast one object of a predetermined map of the environment of theapparatus to provide correlated target information. Yet further, theapparatus includes means for storing the correlated target informationfor the at least one object in an electronic database.

In a fifth aspect, another apparatus is provided. In some embodiments,the apparatus includes means for transmitting at least two signalpulses. The apparatus further includes for each transmitted signalpulse, means for receiving a reflection signal associated withreflection of the respective transmitted signal pulse. Each reflectionsignal may be received when the apparatus is in a different respectivelocation. Additionally, the apparatus includes means for processing thereceived reflection signals to determine target information relating toone or more targets in an environment of the apparatus. Also, theapparatus includes means for correlating the target information withpredetermined target information to provide correlated targetinformation. Yet further, the apparatus includes means for determining alocation of the apparatus based on the correlated target information.And, the apparatus also includes means for controlling an autonomousvehicle based on the determined location of the apparatus.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a vehicle, accordingto an example embodiment.

FIG. 2 shows a vehicle, according to an example embodiment.

FIG. 3A is a top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 3B is another top view of an autonomous vehicle operating scenario,according to an example embodiment.

FIG. 3C is a view of map, according to an example embodiment.

FIG. 4A shows a method, according to an example embodiment.

FIG. 4B shows a method, according to an example embodiment.

FIG. 5 is a schematic diagram of a computer program product, accordingto an example embodiment.

DETAILED DESCRIPTION

Example methods and systems are described herein. Any example embodimentor feature described herein is not necessarily to be construed aspreferred or advantageous over other embodiments or features. Theexample embodiments described herein are not meant to be limiting. Itwill be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

Furthermore, the particular arrangements shown in the Figures should notbe viewed as limiting. It should be understood that other embodimentsmay include more or less of each element shown in a given Figure.Further, some of the illustrated elements may be combined or omitted.Yet further, an example embodiment may include elements that are notillustrated in the Figures.

1. Overview

Example embodiments disclosed herein relate to radar systems in anautonomous vehicle. Some methods disclosed herein could be carried outin part or in full by a vehicle configured to operate in an autonomousmode with or without external interaction (e.g., such as from a user ofthe vehicle). Further, the embodiments disclosed herein may also be usedto help optimize the radar system based on the movement of theautonomous vehicle.

The radar system of the autonomous vehicle may feature a plurality ofantennas. Each antenna may be configured to (i) transmit electromagneticsignals, (ii) receive electromagnetic signals, or (iii) both transmitand receive electromagnetic signals. The antennas may form an array ofantenna elements. The array may be able to steer a beam formed by thetransmitted electromagnetic signals. Additionally, the array may aid indetecting the direction from which electromagnetic signals are received.

The radar system further contains a processor configured to process thereceived signals. The received signals may be reflected from objectswithin the field of view of the radar system. The reflected signals maybe stored as data for processing by the radar system. The processor maybe configured to located objects within the field of view of the radarsystem. For example, the processor in the radar system may calculate adistance and a direction to one or more objects within the field of viewof the radar system.

Additionally, the autonomous vehicle may have one or moreoutput-indication sensors configured to measure a movement of thevehicle. Such output-indication sensors could include, for example,sensors that monitor the wheel speed of the vehicle, the steeringposition, and/or the current location of the vehicle (e.g., a GlobalPositioning System).

Within the context of the disclosure, the processor in the radar systemmay use data associated with the output-indication sensors to adjust thedetermination of the distance and the direction to each object withinthe field of view of the radar system.

One aspect of the present disclosure provides a method for the operationof a vehicular radar system for use with location determinationfunctions of a vehicle. The presently disclosed system can use the radarsystem to capture data of features of a roadside along which the vehiclemay be traveling. That is, the radar may operate in a directiongenerally perpendicular to the direction of travel of the vehicle. Thecaptured data may be used to both (i) associate radar information withknown map data and (ii) to determine a location of the vehicle based onradar data. In order to capture the radar data, the radar system of thevehicle may operate in a Synthetic Aperture Radar (SAR) mode.

To operate in a SAR mode, a radar system of the vehicle may transmit andreceive multiple radar pulses. The radar pulses may be transmitted andreceived while the vehicle is in motion. Thus, the radar pulses may betransmitted and received from different locations. A SAR radar systemprovides advantages of traditional scanning radar systems due to thetransmitting and receiving being performed at multiple locations. Theradar system may simultaneously (or in parallel) process severalreceived signals. Each received signal may contain information about avariety of radar targets within a field of view of the radar system.Because the signals were transmitted and received from differentlocations, each received signal may contain different information aboutthe variety of radar targets due to the signals being reflected from thetarget objects at different angles relative to the radar unit of thevehicle. By receiving the signals from different angles, the radarsystem may have a higher resolution than traditional scanning radarsystems.

In some examples, the radar system may be configured to interrogate(i.e. transmit radar signals) in a direction normal to the direction oftravel of the vehicle. Thus, the radar system may be able to determineinformation about roadside object along which the vehicle passes. Insome examples, this information may be two dimensional (e.g. distancesvarious objects are from the roadside). In other examples, thisinformation may be three dimensional (e.g. a point cloud of variousportions of detected objects). Thus, the vehicle may be able to “map”the side of the road as it drives along.

In one example, the vehicle may be configured with features that allowthe vehicle to determine its location, such as global positioning system(GPS) and maps. During operation of the vehicle, a processing unit(either on the vehicle itself or located remotely) may receive bothposition information, such as that from GPS, and the radar information.Based on the position information and the radar information, theprocessing unit may be able to correlate the radar information with amap and the position information. That is, roadside features that may bepresent in the map may be identified based on the radar information. Forexample, radar information may be able to indicate the presence ofbuildings, trees, roadways, etc. that are present on the map. Theprocessing unit may store the radar data and corresponding correlationin a database

In another example, a vehicle may be configured with features that allowthe vehicle to determine its location, such as a radar system and maps.The maps may include radar information that is correlated with locationson the maps. During the operation of the vehicle, the radar unit mayreceive radar information from alongside the roadway of the vehicle.This radar information may be used by a processing unit to determine thelocation of the vehicle based on the correlated map data. Therefore, thevehicle may be able to locate itself without the used of GPS or otherlocation service. The radar unit (in combination with some furtherprocessing) may be able to provide vehicular location information.

Additionally, the vehicle could be operated in a safety mode. The safetymode could represent an autonomous, semi-autonomous, or manual mode inwhich the vehicle may be controlled to operate in a safe fashion. Suchsafety modes of operation could include the vehicle autonomously pullingover to the side of a road and/or the vehicle returning some or alloperational control of the vehicle to a driver or another controlsystem.

A server, such as one or more nodes of a server network, couldadditionally or alternatively carry out the methods disclosed herein inpart or in full. In an example embodiment, a server or computer mayreceive both (i) data associated with the output-indication sensors and(ii) data related to the received signals. Such data associated with theoutput-indication sensors could include any current parameters of thevehicle (e.g., velocity, acceleration, steering position). Further, theserver may already know (or be able to calculate) information related tothe current parameters. Further, the server may also receive (or alreadyhave stored) the data related to the received signals.

Also disclosed herein are non-transitory computer readable media withstored instructions. The instructions could be executable by a computingdevice to cause the computing device to perform functions similar tothose described in the aforementioned methods.

2. Example Systems

Example systems within the scope of the present disclosure will now bedescribed in greater detail. An example system may be implemented in ormay take the form of an automobile. However, an example system may alsobe implemented in or take the form of other vehicles, such as cars,trucks, motorcycles, buses, boats, airplanes, helicopters, lawn mowers,earth movers, boats, snowmobiles, aircraft, recreational vehicles,amusement park vehicles, farm equipment, construction equipment, trams,golf carts, trains, and trolleys. Other vehicles are possible as well.

FIG. 1 is a functional block diagram illustrating a vehicle 100,according to an example embodiment. The vehicle 100 could be configuredto operate fully or partially in an autonomous mode. For example, acomputer system could control the vehicle 100 while in the autonomousmode, and may be operable to transmit a radio signal, receive reflectedradio signals with at least one antenna in the radar system, process thereceived reflected radio signals, locate the objects that caused thereflections, calculate an angle and a distance to each object thatreflected the radio signal, and calculate an unambiguous angleassociated with the angle. While in autonomous mode, the vehicle 100 maybe configured to operate without human interaction.

The vehicle 100 could include various subsystems such as a propulsionsystem 102, a sensor system 104, a control system 106, one or moreperipherals 108, as well as a power supply 110, a computer system 112, adata storage 114, and a user interface 116. The vehicle 100 may includemore or fewer subsystems and each subsystem could include multipleelements. Further, each of the subsystems and elements of vehicle 100could be interconnected. Thus, one or more of the described functions ofthe vehicle 100 may be divided up into additional functional or physicalcomponents, or combined into fewer functional or physical components. Insome further examples, additional functional and/or physical componentsmay be added to the examples illustrated by FIG. 1.

The propulsion system 102 may include components operable to providepowered motion for the vehicle 100. Depending upon the embodiment, thepropulsion system 102 could include an engine/motor 118, an energysource 119, a transmission 120, and wheels/tires 121. The engine/motor118 could be any combination of an internal combustion engine, anelectric motor, steam engine, Stirling engine. Other motors and/orengines are possible. In some embodiments, the engine/motor 118 may beconfigured to convert energy source 119 into mechanical energy. In someembodiments, the propulsion system 102 could include multiple types ofengines and/or motors. For instance, a gas-electric hybrid car couldinclude a gasoline engine and an electric motor. Other examples arepossible.

The energy source 119 could represent a source of energy that may, infull or in part, power the engine/motor 118. Examples of energy sources119 contemplated within the scope of the present disclosure includegasoline, diesel, other petroleum-based fuels, propane, other compressedgas-based fuels, ethanol, solar panels, batteries, and other sources ofelectrical power. The energy source(s) 119 could additionally oralternatively include any combination of fuel tanks, batteries,capacitors, and/or flywheels. The energy source 118 could also provideenergy for other systems of the vehicle 100.

The transmission 120 could include elements that are operable totransmit mechanical power from the engine/motor 118 to the wheels/tires121. The transmission 120 could include a gearbox, a clutch, adifferential, and a drive shaft. Other components of transmission 120are possible. The drive shafts could include one or more axles thatcould be coupled to the one or more wheels/tires 121.

The wheels/tires 121 of vehicle 100 could be configured in variousformats, including a unicycle, bicycle/motorcycle, tricycle, orcar/truck four-wheel format. Other wheel/tire geometries are possible,such as those including six or more wheels. Any combination of thewheels/tires 121 of vehicle 100 may be operable to rotate differentiallywith respect to other wheels/tires 121. The wheels/tires 121 couldrepresent at least one wheel that is fixedly attached to thetransmission 120 and at least one tire coupled to a rim of the wheelthat could make contact with the driving surface. The wheels/tires 121could include any combination of metal and rubber. Other materials arepossible.

The sensor system 104 may include several elements such as a GlobalPositioning System (GPS) 122, ultrasonic sensors (not shown), aninertial measurement unit (IMU) 124, a radar 126, a laserrangefinder/LIDAR 128, a camera 130, a steering sensor 123, and athrottle/brake sensor 125. The sensor system 104 could also includeother sensors, such as those that may monitor internal systems of thevehicle 100 (e.g., 02 monitor, fuel gauge, engine oil temperature, brakewear).

The GPS 122 could include a transceiver operable to provide informationregarding the position of the vehicle 100 with respect to the Earth. TheIMU 124 could include a combination of accelerometers and gyroscopes andcould represent any number of systems that sense position andorientation changes of a body based on inertial acceleration.Additionally, the IMU 124 may be able to detect a pitch and yaw of thevehicle 100. The pitch and yaw may be detected while the vehicle isstationary or in motion.

The radar 126 may represent a system that utilizes radio signals tosense objects, and in some cases their speed and heading, with respectto the local environment of the vehicle 100. The radar 126 may includeboth a transmitter and a receiver (shown as TX/RX 127 in FIG. 1).Additionally, the radar 126 may have a plurality of antennas configuredto transmit and receive radio signals. The laser rangefinder/LIDAR 128could include one or more laser sources, a laser scanner, and one ormore detectors, among other system components. The laserrangefinder/LIDAR 128 could be configured to operate in a coherent mode(e.g., using heterodyne detection) or in an incoherent detection mode.The camera 130 could include one or more devices configured to capture aplurality of images of the environment of the vehicle 100. The camera130 could be a still camera or a video camera.

The steering sensor 123 may represent a system that senses the steeringangle of the vehicle 100. In some embodiments, the steering sensor 123may measure the angle of the steering wheel itself. In otherembodiments, the steering sensor 123 may measure an electrical signalrepresentative of the angle of the steering wheel. Still, in furtherembodiments, the steering sensor 123 may measure an angle of the wheelsof the vehicle 100. For instance, an angle of the wheels with respect toa forward axis of the vehicle 100 could be sensed. Additionally, in yetfurther embodiments, the steering sensor 123 may measure a combination(or a subset) of the angle of the steering wheel, electrical signalrepresenting the angle of the steering wheel, and the angle of thewheels of vehicle 100.

The throttle/brake sensor 125 may represent a system that senses theposition of either the throttle position or brake position of thevehicle 100. In some embodiments, separate sensors may measure thethrottle position and brake position. In some embodiments, thethrottle/brake sensor 125 may measure the angle of both the gas pedal(throttle) and brake pedal. In other embodiments, the throttle/brakesensor 125 may measure an electrical signal that could represent, forinstance, an angle of a gas pedal (throttle) and/or an angle of a brakepedal. Still, in further embodiments, the throttle/brake sensor 125 maymeasure an angle of a throttle body of the vehicle 100. The throttlebody may include part of the physical mechanism that provides modulationof the energy source 119 to the engine/motor 118 (e.g., a butterflyvalve or carburetor). Additionally, the throttle/brake sensor 125 maymeasure a pressure of one or more brake pads on a rotor of vehicle 100.In yet further embodiments, the throttle/brake sensor 125 may measure acombination (or a subset) of the angle of the gas pedal (throttle) andbrake pedal, electrical signal representing the angle of the gas pedal(throttle) and brake pedal, the angle of the throttle body, and thepressure that at least one brake pad is applying to a rotor of vehicle100. In other embodiments, the throttle/brake sensor 125 could beconfigured to measure a pressure applied to a pedal of the vehicle, suchas a throttle or brake pedal.

The control system 106 could include various elements include steeringunit 132, throttle 134, brake unit 136, a sensor fusion algorithm 138, acomputer vision system 140, a navigation/pathing system 142, and anobstacle avoidance system 144. The steering unit 132 could represent anycombination of mechanisms that may be operable to adjust the heading ofvehicle 100. The throttle 134 could control, for instance, the operatingspeed of the engine/motor 118 and thus control the speed of the vehicle100. The brake unit 136 could be operable to decelerate the vehicle 100.The brake unit 136 could use friction to slow the wheels/tires 121. Inother embodiments, the brake unit 136 could convert the kinetic energyof the wheels/tires 121 to electric current.

A sensor fusion algorithm 138 could include, for instance, a Kalmanfilter, Bayesian network, or other algorithm that may accept data fromsensor system 104 as input. The sensor fusion algorithm 138 couldprovide various assessments based on the sensor data. Depending upon theembodiment, the assessments could include evaluations of individualobjects and/or features, evaluation of a particular situation, and/orevaluate possible impacts based on the particular situation. Otherassessments are possible.

The computer vision system 140 could include hardware and softwareoperable to process and analyze images in an effort to determineobjects, important environmental features (e.g., stop lights, road wayboundaries, etc.), and obstacles. The computer vision system 140 coulduse object recognition, Structure From Motion (SFM), video tracking, andother algorithms used in computer vision, for instance, to recognizeobjects, map an environment, track objects, estimate the speed ofobjects, etc.

The navigation/pathing system 142 could be configured to determine adriving path for the vehicle 100. The navigation/pathing system 142 mayadditionally update the driving path dynamically while the vehicle 100is in operation. In some embodiments, the navigation/pathing system 142could incorporate data from the sensor fusion algorithm 138, the GPS122, and known maps so as to determine the driving path for vehicle 100.The navigation/pathing system 142 may also use radar and map data 117 inorder to navigate and determine a path for the vehicle.

The obstacle avoidance system 144 could represent a control systemconfigured to evaluate potential obstacles based on sensor data andcontrol the vehicle 100 to avoid or otherwise negotiate the potentialobstacles.

Various peripherals 108 could be included in vehicle 100. For example,peripherals 108 could include a wireless communication system 146, atouchscreen 148, a microphone 150, and/or a speaker 152. The peripherals108 could provide, for instance, means for a user of the vehicle 100 tointeract with the user interface 116. For example, the touchscreen 148could provide information to a user of vehicle 100. The user interface116 could also be operable to accept input from the user via thetouchscreen 148. In other instances, the peripherals 108 may providemeans for the vehicle 100 to communicate with devices within itsenvironment.

In one example, the wireless communication system 146 could beconfigured to wirelessly communicate with one or more devices directlyor via a communication network. For example, wireless communicationsystem 146 could use 3G cellular communication, such as CDMA, EVDO,GSM/GPRS, or 4G cellular communication, such as WiMAX or LTE.Alternatively, wireless communication system 146 could communicate witha wireless local area network (WLAN), for example, using WiFi. In someembodiments, wireless communication system 146 could communicatedirectly with a device, for example, using an infrared link, Bluetooth,or ZigBee. Other wireless protocols, such as various vehicularcommunication systems, are possible within the context of thedisclosure. For example, the wireless communication system 146 couldinclude one or more dedicated short range communications (DSRC) devicesthat could include public and/or private data communications betweenvehicles and/or roadside stations.

The power supply 110 may provide power to various components of vehicle100 and could represent, for example, a rechargeable lithium-ion orlead-acid battery. In an example embodiment, one or more banks of suchbatteries could be configured to provide electrical power. Other powersupply materials and types are possible. Depending upon the embodiment,the power supply 110, and energy source 119 could be integrated into asingle energy source, such as in some all-electric cars.

Many or all of the functions of vehicle 100 could be controlled bycomputer system 112. Computer system 112 may include at least oneprocessor 113 (which could include at least one microprocessor) thatexecutes instructions 115 stored in a non-transitory computer readablemedium, such as the data storage 114. The computer system 112 may alsorepresent a plurality of computing devices that may serve to controlindividual components or subsystems of the vehicle 100 in a distributedfashion.

In some embodiments, data storage 114 may contain instructions 115(e.g., program logic) executable by the processor 113 to execute variousfunctions of vehicle 100, including those described herein in connectionwith FIGS. 4A and 4B. Data storage 114 may contain additionalinstructions as well, including instructions to transmit data to,receive data from, interact with, and/or control one or more of thepropulsion system 102, the sensor system 104, the control system 106,and the peripherals 108.

In addition to the instructions 115, the data storage 114 may store datasuch as roadway maps, path information, among other information. As partof the roadway map information, the data storage 114 may include radarreflection information related to the roadway map. For example, theradar reflection or signature of various objected may stored andcorrelated to various points on a map. Such information may be used byvehicle 100 and computer system 112 at during the operation of thevehicle 100 in the autonomous, semi-autonomous, and/or manual modes.

The vehicle 100 may include a user interface 116 for providinginformation to or receiving input from a user of vehicle 100. The userinterface 116 could control or enable control of content and/or thelayout of interactive images that could be displayed on the touchscreen148. Further, the user interface 116 could include one or moreinput/output devices within the set of peripherals 108, such as thewireless communication system 146, the touchscreen 148, the microphone150, and the speaker 152.

The computer system 112 may control the function of the vehicle 100based on inputs received from various subsystems (e.g., propulsionsystem 102, sensor system 104, and control system 106), as well as fromthe user interface 116. For example, the computer system 112 may utilizeinput from the sensor system 104 in order to estimate the outputproduced by the propulsion system 102 and the control system 106.Depending upon the embodiment, the computer system 112 could be operableto monitor many aspects of the vehicle 100 and its subsystems. In someembodiments, the computer system 112 may disable some or all functionsof the vehicle 100 based on signals received from sensor system 104.

The components of vehicle 100 could be configured to work in aninterconnected fashion with other components within or outside theirrespective systems. For instance, in an example embodiment, the camera130 could capture a plurality of images that could represent informationabout a state of an environment of the vehicle 100 operating in anautonomous mode. The state of the environment could include parametersof the road on which the vehicle is operating. For example, the computervision system 140 may be able to recognize the slope (grade) or otherfeatures based on the plurality of images of a roadway. Additionally,the combination of Global Positioning System 122 and the featuresrecognized by the computer vision system 140 may be used with map datastored in the data storage 114 to determine specific road parameters.Further, the radar unit 126 may also provide information about thesurroundings of the vehicle.

In other words, a combination of various sensors (and the computersystem 112) could interact to provide an indication of an input providedto control a vehicle or an indication of the surroundings of a vehicle.

The computer system 112 could carry out several determinations based onthe received radar signals. For example, the computer system 112 couldcalculate a location of the vehicle based on the electromagnetic signalsand data stored in a map. Additionally, the computer system 112 couldstore data based on received electromagnetic signals and a currentlocation of the vehicle along with the map data 117. By storing the databased on received electromagnetic signals, the vehicle may be able tolocate itself in the future based on received electromagnetic signals.

In one scenario, the radar unit 126 may receive a plurality of radarsignals from a plurality of target objects within the field of view ofthe radar. The field of view of the radar may generally be in adirection perpendicular to the direction of travel of the vehicle. Thus,the radar may be interrogating a roadside of the road along which thevehicle is driving. Additionally, the radar unit 126 may transmit datarelating to the plurality of received radar signals to the computersystem 112. Further, the computer system 112 may also receive mappingdata. For example, the computer system 112 may receive mapping data thatmay (or may not) have associated radar reflection data. Thus, thecomputer system 112 may correlate the radar data with the mapping data.

Although FIG. 1 shows various components of vehicle 100, i.e., wirelesscommunication system 146, computer system 112, data storage 114, anduser interface 116, as being integrated into the vehicle 100, one ormore of these components could be mounted or associated separately fromthe vehicle 100. For example, data storage 114 could, in part or infull, exist separate from the vehicle 100. Thus, the vehicle 100 couldbe provided in the form of device elements that may be locatedseparately or together. The device elements that make up vehicle 100could be communicatively coupled together in a wired and/or wirelessfashion.

FIG. 2 shows a vehicle 200 that could be similar or identical to vehicle100 described in reference to FIG. 1. Depending on the embodiment,vehicle 200 could include a sensor unit 202, a wireless communicationsystem 204, a radar 206, a laser rangefinder 208, and a camera 210. Theelements of vehicle 200 could include some or all of the elementsdescribed for FIG. 1. Although vehicle 200 is illustrated in FIG. 2 as acar, other embodiments are possible. For instance, the vehicle 200 couldrepresent a truck, a van, a semi-trailer truck, a motorcycle, a golfcart, an off-road vehicle, or a farm vehicle, among other examples.

The sensor unit 202 could include one or more different sensorsconfigured to capture information about an environment of the vehicle200. For example, sensor unit 202 could include any combination ofcameras, radars, LIDARs, range finders, and acoustic sensors. Othertypes of sensors are possible. Depending on the embodiment, the sensorunit 202 could include one or more movable mounts that could be operableto adjust the orientation of one or more sensors in the sensor unit 202.In one embodiment, the movable mount could include a rotating platformthat could scan sensors so as to obtain information from each directionaround the vehicle 200. In another embodiment, the movable mount of thesensor unit 202 could be moveable in a scanning fashion within aparticular range of angles and/or azimuths. The sensor unit 202 could bemounted atop the roof of a car, for instance, however other mountinglocations are possible. Additionally, the sensors of sensor unit 202could be distributed in different locations and need not be collocatedin a single location. Some possible sensor types and mounting locationsinclude radar 206 and laser rangefinder 208.

The wireless communication system 204 could be located as depicted inFIG. 2. Alternatively, the wireless communication system 204 could belocated, fully or in part, elsewhere. The wireless communication system204 may include wireless transmitters and receivers that could beconfigured to communicate with devices external or internal to thevehicle 200. Specifically, the wireless communication system 204 couldinclude transceivers configured to communicate with other vehiclesand/or computing devices, for instance, in a vehicular communicationsystem or a roadway station. Examples of such vehicular communicationsystems include dedicated short range communications (DSRC), radiofrequency identification (RFID), and other proposed communicationstandards directed towards intelligent transport systems.

The camera 210 could be mounted inside a front windshield of the vehicle200. The camera 210 could be configured to capture a plurality of imagesof the environment of the vehicle 200. Specifically, as illustrated, thecamera 210 could capture images from a forward-looking view with respectto the vehicle 200. Other mounting locations and viewing angles ofcamera 210 are possible. The camera 210 could represent one or morevisible light cameras. Alternatively or additionally, camera 210 couldinclude infrared sensing capabilities. The camera 210 could haveassociated optics that could be operable to provide an adjustable fieldof view. Further, the camera 210 could be mounted to vehicle 200 with amovable mount that could be operable to vary a pointing angle of thecamera 210.

FIG. 3A illustrates a scenario 300 involving a vehicle 302 travelingdown a roadway 304. A vehicle 302 could be operating in an autonomousmode. Further, the vehicle 302 may be configured with a radar unit 310.The radar unit 310 may be configured with a plurality of antennaelements. In the particular embodiment shown in FIGS. 3A and 3B, theradar unit has an antenna beam 306 pointed toward the side of the roadof the passenger side of the vehicle. As shown, the antennas transmit aradar signal by the antenna beam 306 that is generally perpendicular tothe direction of travel of the vehicle 302. However, in some examples,the antenna beam 306 may be a scanning beam that does not always pointin the same direction. Further, the radar unit 310 may also be able toreceive reflected radar signals. The radar signals received by the radarunit 310 may be received based on the antenna beam 306. That is, radarsignals may only be received in the direction of antenna beam 306.

In one example driving situation 330, shown in FIG. 3B, the vehicle 302may be traveling in the direction indicated by the pathway 312 to end atvehicle position 308. As the vehicle is traveling, it may transmit radarsignals based on antenna beam 306. In one embodiment, as the vehiclemoves forwards, the signals reflected back to the vehicle, may bereceived by the antenna unit based on the antenna beam 306 from variousdifferent positions as the vehicle travels pathway 312. By receivingsignals at a variety of different positions, the radar receivingantennas of the vehicle may create a virtual antenna aperture that ismuch larger than the physical antenna aperture of the vehicle. Operatingthe radar system of the vehicle in this manner may be known as a SARmode.

Additionally, in some examples the radar unit 310 may contain aprocessor (different from processor 113 of FIG. 1) that converts thereceived signals into data representative of the received signals. Thedata may be used to create a two dimensional or three dimensional imagerepresentative of the radar reflections. The image may include objectsthat are located on the side of the roadway. In some examples, the radarunit may correlate the objects that cause the reflections with objectsor locations on a map. The processor may store these correlations in adatabase or memory, such as data storage 114 of FIG. 1. In some otherexamples, the processor may correlate the objects that cause thereflections with objects or locations on a map to determine a locationof the vehicle. The vehicle may then use this location in the vehicle'sguidance.

In the example shown in FIG. 3B, the antenna array may transmit a radiosignal and receives a portion of the transmitted radio signal that hasreflected from an object in the environment of vehicle 302. Objects314-318 may each reflect radar signals transmitted by the antenna of theradar system of the vehicle. When the antenna of the radar system of thevehicle receives these reflections it may be able to determine what theobjects are. The objects may be identified based on either their radarreflections or correlating the radar reflections with map data. In someexamples, the objects may be trees, road signs, street lights,driveways, other roads, guard rails, or other roadside objects.

FIG. 3C shows an example map 350. The example map may include variousstreets and include various objects, such as objects 314-318 also shownin FIG. 3B. The vehicle may use a map, such as map 350, to aid in thevehicle's navigation.

The vehicle may use data from the radar system (e.g. as in scenario 330shown in FIG. 3B) to create radar data signatures for the variousobjects, such as objects 314-318. When radar data signatures for thevarious objects are created, the signature may be stored in a database.The signature may correspond with a location on the map, an object onthe map, or both the location and object. Thus, once the databasecontains sufficient radar signatures for the objects, the vehicle may beable to locate itself based on detecting objects next to the road.

For example, the vehicle may receive radar data that corresponds to theradar signatures for objects 316-318. Based on the radar signatures, thevehicle may be able to determine it is at position 320. Therefore, thevehicle may be able to locate itself within the map 350 (or within anenvironment of the vehicle) based on radar data. The radar data may beobtained in a direction that is perpendicular to the direction of travelfor the vehicle.

3. Example Methods

A method 400, shown in FIG. 4A, is provided for transmitting, by a radarunit of a vehicle, at least two signal pulses, for each transmittedsignal pulse, receiving, by the radar unit, a reflection signalassociated with reflection of the respective transmitted signal pulse,wherein each reflection signal is received when the vehicle is in adifferent respective location, processing the received reflectionsignals to determine target information relating to one or more targetsin an environment of the vehicle, correlating the target informationwith at least one object of a predetermined map of the environment ofthe vehicle to provide correlated target information, and storing thecorrelated target information for the at least one object in anelectronic database.

A method 450, shown in FIG. 4B, is provided for transmitting, by a radarunit of a vehicle, at least two signal pulses, for each transmittedsignal pulse, receiving, by the radar unit, a reflection signalassociated with reflection of the respective transmitted signal pulse,wherein each reflection signal is received when the vehicle is in adifferent respective location, processing the received reflectionsignals to determine target information relating to one or more targetsin an environment of the vehicle, correlating the target informationwith at least one object of a predetermined map of the environment ofthe vehicle to provide correlated target information, determining alocation of the vehicle based on the correlated target information, andcontrolling an autonomous vehicle based on the determined location ofthe vehicle.

The methods could be performed using any of the apparatus shown in FIGS.1-3B and described above; however, other configurations could be used.FIGS. 4A and 4B illustrate the steps in an example method, however, itis understood that in other embodiments, the steps may appear indifferent order and steps could be added, subtracted, or modified.Additionally, the steps may be performed in a linear manner (as shown)or may be performed in a parallel manner (not shown).

Block 402 of FIG. 4A includes transmitting, by a radar unit of avehicle, at least two signal pulses. The vehicle described in thismethod could be the vehicle 100 and/or vehicle 200 as illustrated anddescribed in reference to FIGS. 1 and 2, respectively. The radar unit ofthe vehicle may transmit the signal pulses accord to many differentradar encoding schemes. The present disclosure is not limited to onespecific radar encoding scheme. The at least two signal pulses may betransmitted from the radar unit while the vehicle is in a singleposition. In a different example, the at least two signal pulses may betransmitted from the radar unit while the vehicle is in motion so thepulses are transmitted from different positions. The at least two signalpulses may be transmitted in a direction that is generally perpendicularto the direction of travel of the vehicle. For example, the two signalpulses may be transmitted in a direction of a passenger side of thevehicle.

Block 404 includes, for each transmitted signal pulse, receiving, by theradar unit, a reflection signal associated with reflection of therespective transmitted signal pulse, wherein each reflection signal isreceived when the vehicle is in a different respective location.Receiving the reflection signal includes receiving radio signals thatare reflected from one or more objects in the field of view of the radarsystem. The reflection signals may be received by the radar unit of thevehicle while the vehicle is different locations. For example, the radarunit may receive the reflection signals as the vehicle is travelingalong a roadway. As previously discussed, by receiving signals at avariety of different positions, the radar receiving antennas of thevehicle may create a virtual antenna aperture that is much larger thanthe physical antenna aperture of the vehicle. Therefore, the signals maybe received at a variety of locations and the radar unit may beoperating in a SAR mode.

A processor in the radar system may convert the received radio signalsinto data to relay for further processing. For example, the radar systemmay transmit a signal and receive a set of reflected signals back. Theradar system may further identify distance and direction information toeach object that causes reflections back to the vehicle.

Block 406 includes, processing the received reflection signals todetermine target information relating to one or more targets in anenvironment of the vehicle. Depending upon the embodiment, the reflectedsignals may be processed fully or in part by a server and communicatedto the vehicle. The processing may include creating a two or threedimensional image based on the reflection signals. The image maycorrespond to a field of view of the radar unit. Because the radarsystem may operate in a SAR mode, the resolution of the radar may bebetter than the resolution of a radar unit that is not operating in aSAR mode.

Block 408 includes correlating the target information with at least oneobject of a predetermined map of the environment of the vehicle toprovide correlated target information. Correlating the targetinformation may include mapping radar data indexed with information froma map. For example, the map may include objects that are located alongthe roadside. The radar reflection (i.e. radar signatures) of thevarious objects may be correlated with the respective objects. Inanother example, the correlation may correlate radar reflections with aknown location of the vehicle (and omit object information from themap). Correlating the target information may include associating thetarget information with one or more locations based on a globalpositioning system (GPS) signal. Thus, through the correlation, a mapmay be created of the radar signatures of the roadside. In someexamples, the correlation may be made with respect to both known mapobjects as well as a known vehicle position.

Block 410 includes storing the correlated target information for the atleast one object in an electronic database. The correlated targetinformation may be stored in an electronic database in order to allowthe database to be queried at a later time. The stored correlated targetinformation may be used at a later time to determine a location of avehicle based on a radar scan of a roadside. The correlated targetinformation may be stored in a manner that associates the correlatedtarget information with a specific location of a map and/or roadway.

Block 452 of FIG. 4B includes transmitting, by a radar unit of avehicle, at least two signal pulses. The vehicle described in thismethod could be the vehicle 100 and/or vehicle 200 as illustrated anddescribed in reference to FIGS. 1 and 2, respectively. The radar unit ofthe vehicle may transmit the signal pulses accord to many differentradar encoding schemes. The present disclosure is not limited to onespecific radar encoding scheme. The at least two signal pulses may betransmitted from the radar unit while the vehicle is in a singleposition. In a different example, the at least two signal pulses may betransmitted from the radar unit while the vehicle is in motion so thepulses are transmitted from different positions. The at least two signalpulses may be transmitted in a direction that is generally perpendicularto the direction of travel of the vehicle. For example, the two signalpulses may be transmitted in a direction of a passenger side of thevehicle.

Block 454 includes, for each transmitted signal pulse, receiving, by theradar unit, a reflection signal associated with reflection of therespective transmitted signal pulse, wherein each reflection signal isreceived when the vehicle is in a different respective location.Receiving the reflection signal includes receiving radio signals thatare reflected from one or more objects in the field of view of the radarsystem. The reflection signals may be received by the radar unit of thevehicle while the vehicle is different locations. For example, the radarunit may receive the reflection signals as the vehicle is travelingalong a roadway. As previously discussed, by receiving signals at avariety of different positions, the radar receiving antennas of thevehicle may create a virtual antenna aperture that is much larger thanthe physical antenna aperture of the vehicle. Therefore, the signals maybe received at a variety of locations and the radar unit may beoperating in a SAR mode.

A processor in the radar system may convert the received radio signalsinto data to relay for further processing. For example, the radar systemmay transmit a signal and receive a set of reflected signals back. Theradar system may further identify distance and direction information toeach object that causes reflections back to the vehicle.

Block 456 includes, processing the received reflection signals todetermine target information relating to one or more targets in anenvironment of the vehicle. Depending upon the embodiment, the reflectedsignals may be processed fully or in part by a server and communicatedto the vehicle. The processing may include creating a two or threedimensional image based on the reflection signals. The image maycorrespond to a field of view of the radar unit. Because the radarsystem may operate in a SAR mode, the resolution of the radar may bebetter than the resolution of a radar unit that is not operating in aSAR mode.

Block 458 includes correlating the target information with at least oneobject of a predetermined map of the environment of the vehicle toprovide correlated target information. Correlating the targetinformation may include mapping radar data indexed with information froma map. For example, the map may include objects that are located alongthe roadside. The radar reflection (i.e. radar signatures) of thevarious objects may be correlated with the respective objects.

Block 460 includes determining a location of the vehicle based on thecorrelated target information. The vehicle may have a database thatincludes location information based on correlated target information.Thus, by comparing the correlated target information with stored targetinformation the database may be used to determine a location of thevehicle. For example, the correlated target information may include atree, street sign, and light pole. Based on a radar signature matchingthe correlated target information, the location where the radar unitreceived the reflections can be determined. Thus, the roadside objectsthat cause radar reflections may be correlated to map data to determinethe vehicle's location.

Block 462 includes controlling an autonomous vehicle based on thedetermined location of the vehicle. Because the location of the vehiclewas determined at block 460, this location information may be used withthe navigation system of the vehicle to autonomously control thevehicle. While operating in the autonomous mode, the vehicle may use acomputer system to control the operation of the vehicle withlittle-to-no human input. For example, a human-operator may enter anaddress into an autonomous vehicle and the vehicle may then be able todrive, without further input from the human (e.g., the human does nothave to steer or touch the brake/gas pedals), to the specifieddestination.

While the vehicle is operating autonomously, the sensor system may bereceiving data about the environment of the vehicle from the radarsystem. The processing system of the vehicle may alter the control ofthe vehicle based on data received from the various sensors. In someexamples, the autonomous vehicle may alter a velocity of the autonomousvehicle in response to data from the various sensors. The autonomousvehicle may change velocity in order to avoid obstacles, obey trafficlaws, etc. When a processing system in the vehicle identifies objectsnear the autonomous vehicle, the vehicle may be able to change velocity,or alter the movement in another way. The location information used bythe vehicle may be provided by the methods and systems disclosed herein.

Example methods, such as method 400 of FIG. 4A and method 450 of FIG.4B, may be carried out in whole or in part by the vehicle and itssubsystems. Accordingly, example methods could be described by way ofexample herein as being implemented by the vehicle. However, it shouldbe understood that an example method may be implemented in whole or inpart by other computing devices. For example, an example method may beimplemented in whole or in part by a server system, which receives datafrom a device such as those associated with the vehicle. Other examplesof computing devices or combinations of computing devices that canimplement an example method are possible.

It will be understood that there are other similar methods that coulddescribe receiving data representative of an electromagnetic signal,receiving an indication of a movement of the vehicle, determining amovement parameter based the indication of the movement of the vehicle,and recovering the distance and direction information from theelectromagnetic signal, based on the movement parameter. Those similarmethods are implicitly contemplated herein.

In some embodiments, the disclosed methods may be implemented ascomputer program instructions encoded on a non-transitorycomputer-readable storage media in a machine-readable format, or onother non-transitory media or articles of manufacture. FIG. 5 is aschematic illustrating a conceptual partial view of an example computerprogram product that includes a computer program for executing acomputer process on a computing device, arranged according to at leastsome embodiments presented herein.

In one embodiment, the example computer program product 500 is providedusing a signal bearing medium 502. The signal bearing medium 502 mayinclude one or more programming instructions 504 that, when executed byone or more processors may provide functionality or portions of thefunctionality described above with respect to FIGS. 1-4B. In someexamples, the signal bearing medium 502 may encompass acomputer-readable medium 506, such as, but not limited to, a hard diskdrive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape,memory, etc. In some implementations, the signal bearing medium 502 mayencompass a computer recordable medium 508, such as, but not limited to,memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations,the signal bearing medium 502 may encompass a communications medium 510,such as, but not limited to, a digital and/or an analog communicationmedium (e.g., a fiber optic cable, a waveguide, a wired communicationslink, a wireless communication link, etc.). Thus, for example, thesignal bearing medium 502 may be conveyed by a wireless form of thecommunications medium 510.

The one or more programming instructions 504 may be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device such as the computer system 112 of FIG. 1may be configured to provide various operations, functions, or actionsin response to the programming instructions 504 conveyed to the computersystem 112 by one or more of the computer readable medium 506, thecomputer recordable medium 508, and/or the communications medium 510.

The non-transitory computer readable medium could also be distributedamong multiple data storage elements, which could be remotely locatedfrom each other. The computing device that executes some or all of thestored instructions could be a vehicle, such as the vehicle 200illustrated in FIG. 2. Alternatively, the computing device that executessome or all of the stored instructions could be another computingdevice, such as a server.

The above detailed description describes various features and functionsof the disclosed systems, devices, and methods with reference to theaccompanying figures. While various aspects and embodiments have beendisclosed herein, other aspects and embodiments will be apparent. Thevarious aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A method comprising: causing, by a computingdevice coupled to a vehicle, a radar system to transmit radar signals inan environment of the vehicle, wherein the vehicle is navigating on aroad in the environment; receiving, at the computing device, first radarreflections corresponding to transmitted radar signals; based on thefirst radar reflections, mapping at least a portion of the road to forma map that represents information about roadside objects; receiving, atthe computing device, second radar reflections corresponding totransmitted radar signals; based on the second radar reflections and themap that represents information about roadside objects, determining alocation of the vehicle relative to one or more roadside objects; andcontrolling the vehicle based on the determined location of the vehicle.2. The method of claim 1, wherein causing the radar system to transmitradar signals comprises: causing the radar system to transmit radarsignals in a direction of a passenger side of the vehicle.
 3. The methodof claim 1, wherein causing the radar system to transmit radar signalscomprises: causing the radar system to transmit radar signals in adirection of a roadside of the road.
 4. The method of claim 1, whereincausing the radar system to transmit radar signals comprises: causingthe radar system to transmit radar signals in a Synthetic Aperture Radar(SAR) mode.
 5. The method of claim 1, further comprising: receiving anindication of a location of the vehicle from a global positioning system(GPS); and storing the map that represents information about theroadside objects with the indication of the location of the vehicle. 6.The method of claim 1, wherein determining the location of the vehiclerelative to one or more roadside objects comprises: detecting one ormore objects based on the second radar reflections; correlating the oneor more objects to one or more roadside objects using the map thatrepresents information about roadside objects; and determining thelocation of the vehicle relative to the one or more roadside objectsbased on correlating the one or more objects to the one or more roadsideobjects.
 7. A system comprising: a vehicle having a radar system; and acomputing device coupled to the vehicle, wherein the computing device isconfigured to: cause the radar system to transmit radar signals in anenvironment of the vehicle, wherein the vehicle is navigating on a roadin the environment; receive first radar reflections corresponding totransmitted radar signals; based on the first radar reflections, map atleast a portion of the road to form a map that represents informationabout roadside objects; receive second radar reflections correspondingto transmitted radar signals; based on the second radar reflections andthe map that represents information about roadside objects, determine alocation of the vehicle relative to one or more roadside objects; andcontrol the vehicle based on the determined location of the vehicle. 8.The system of claim 7, wherein the radar system transmits the radarsignals in a direction of a passenger side of the vehicle.
 9. The systemof claim 7, wherein the radar system transmits the radar signals in adirection of a roadside of the road.
 10. The system of claim 7, whereinthe radar system operates in a Synthetic Aperture Radar (SAR) mode. 11.The system of claim 7, wherein the computing device is furtherconfigured to: receive an indication of a location of the vehicle from aglobal positioning system (GPS); and store the map that representsinformation about the roadside objects with the indication of thelocation of the vehicle.
 12. The system of claim 7, wherein thecomputing device is further configured to: detect one or more objectsbased on the second radar reflections; correlate the one or more objectsto one or more roadside objects using the map that representsinformation about roadside objects; and determine the location of thevehicle relative to the one or more roadside objects based oncorrelating the one or more objects to the one or more roadside objects.13. The system of claim 7, wherein the roadside objects include one ormore road signs, street lights, driveways, or guard rails.
 14. Thesystem of claim 7, wherein the computing device is further configuredto: modify an existing map to include the information about roadsideobjects based on the first radar reflections.
 15. A non-transitorycomputer readable medium having stored therein instructions executableby one or more processors to cause a computing system to performoperations comprising: causing a radar system to transmit radar signalsin an environment of a vehicle, wherein the vehicle is navigating on aroad in the environment; receiving first radar reflections correspondingto transmitted radar signals; based on the first radar reflections,mapping at least a portion of the road to form a map that representsinformation about roadside objects; receiving second radar reflectionscorresponding to transmitted radar signals; based on the second radarreflections and the map that represents information about roadsideobjects, determining a location of the vehicle relative to one or moreroadside objects; and controlling the vehicle based on the determinedlocation of the vehicle.
 16. The non-transitory computer readable mediumof claim 15, wherein the operation of causing the radar system totransmit radar signals comprises: causing the radar system to transmitradar signals in a direction of a passenger side of the vehicle.
 17. Thenon-transitory computer readable medium of claim 15, wherein theoperation of causing the radar system to transmit radar signalscomprises: causing the radar system to transmit radar signals in adirection of a roadside of the road.
 18. The non-transitory computerreadable medium of claim 15, wherein the operation of causing the radarsystem to transmit radar signals comprises: causing the radar system totransmit radar signals in a Synthetic Aperture Radar (SAR) mode.
 19. Thenon-transitory computer readable medium of claim 15, wherein theoperations further comprise: receiving an indication of a location ofthe vehicle from a global positioning system (GPS); and storing the mapthat represents information about the roadside objects with theindication of the location of the vehicle.
 20. The non-transitorycomputer readable medium of claim 15, wherein the operation ofdetermining the location of the vehicle relative to one or more roadsideobjects comprises: detecting one or more objects based on the secondradar reflections; correlating the one or more objects to one or moreroadside objects using the map that represents information aboutroadside objects; and determining the location of the vehicle relativeto the one or more roadside objects based on correlating the one or moreobjects to the one or more roadside objects.